Pump Drive Unit for Water, Oil or Other Fluid Extraction

ABSTRACT

A reciprocating seesaw-type (upward-downward) pump drive unit for water, oil, or other fluid extraction; the pump drive unit uses a pumping rod string that allows pumping fluids from depths of thousands of meters. This unit can be used in any well operated with mechanical pumping, without making any changes to the existing installation, achieving a reduction of around  20 % in pumping and operating equipment costs. The drive unit includes a piston ( 2 ) that slides up and down inside a vertical hydraulic cylinder ( 4 ) with the application of an actuating fluid, and where the piston shaft ( 2 ) is the rod string&#39;s polished rod ( 1 ).

TECHNICAL FIELD

This invention pertains to a reciprocating up and down movement pump drive unit for water, oil, or other fluid extraction; the pump drive unit uses a pumping rod string that allows pumping fluids from depths of thousands of meters. This unit can be used in any well operated with mechanical pumping, without making any changes to the existing installation, achieving a reduction of around 20% in pumping and operating equipment costs.

STATE OF THE TECHNOLOGY AND PROBLEMS TO SOLVE

In relation to the state of the technology, we know that two thirds of the world's extraction wells are operated through mechanical pumping, and that in Argentina alone, approximately 70% of all oil wells are operated using this technology. The growing demand for energy has created a need to optimize pumping facilities in order to level industry costs with international numbers.

Therefore, this invention is intended to reduce operating costs, ensure safety, and protect the environment in fluid pumping operations.

The operational flexibility of the drive unit described in this report is clearly demonstrated at any well that requires mechanical pumping, especially those that need to use pumping units that can provide a broad range of speed variations due to the type of stimulation system involved.

The drive unit is responsible for lifting the rod string and storing pneumatic potential energy, making it possible to work at a very low cycles-per-minute rate, thus allowing complete filling of the pump and a lower dynamic load.

The pumping action achieved with this invention reduces the structural load on the equipment, extending the useful life of the down-hole installation because the pumping rod string works at constant loads.

A drive unit with current technology uses a piston that runs along the inside of a vertical cylinder; this piston has its own drive shaft, which must be connected to the rod string on each side of the shaft and that is separate from the rod string, or is inserted in the pipe or set away from the mouth of the well at a distance equivalent to the length of the stroke so that when the piston is at its maximum elevation, the shaft pokes out of the end of the cylinder for a length equivalent to that of the piston stroke. This produces either a structure that is very long and has little height stability or is complicated to regulate.

On the other hand, in this invention the polished rod of the rod string works as piston shaft, resulting in a greatly simplified drive unit that includes a cylinder with an internal piston attached to the polished rod of the rod string, thus removing the shaft that protrudes from the cylinder and increases the size of the drive unit structure and requires more structural support.

This invention optimizes rod string weight balancing, enabling high sucker rod pulling capacities and a broad range of speed and stroke length variations; its set-up allows independent control of rod string upward and downward speeds, as well as load control.

In addition, there is a significant reduction in weight and volume, facilitating installation and transportation and consequently lowering logistics costs, as the unit can be delivered fully assembled for easy installation that requires only a bull crane. Its size can also be adapted to each individual operation, something that cannot be done with other drive units in the market today.

Another key feature is the ability to adjust operating parameters such as speed and maximum load, and therefore the well's level of operation, acceleration, inversion point are set while the device is running. Furthermore, using a drive unit like the one described in this report allows one to dispense with the use of variable speed drives.

The pump drive unit thus becomes much more efficient because it only uses energy to lift the fluid column and operates the well at a constant level, maximizing its yield.

On the other hand, any risk of fluid spills is eliminated because there is no stuffing box, and in terms of safety or operating risks, there are no exposed moving parts, which eliminates any possibility of personal injury.

BRIEF DESCRIPTION OF THE FIGURES

For an easy understanding of this invention, it has been illustrated with figures depicting one of the preferred methods of implementation as a demonstration, where:

FIG. 1 is a schematic cross-section of the basic elements of a pump drive unit for water, oil or other fluid extraction, according to this invention;

FIG. 2 offers a side view of the pump drive unit according to the invention, with longitudinal tanks surrounding the central cylinder of the unit and a partial lower cross-section;

FIG. 3 shows a view of detail “A” from FIG. 2;

FIG. 4 is a cross-section view of the drive unit's polished rod, with a separator on the threaded end.

In every figure, the same numbers and letters are used to refer to the same elements of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a pump drive unit for extracting fluids from a well, with the polished rod of the rod string (1) actuated alternately by the unit, so as to convey such movement to the fluid pump located deep within the well. The drive unit includes a piston (2) coupled to the polished rod of the rod string (1); this piston (2) is actuated by the pressure of fluid coming in through a pipe (3) so that it will move upward and downward along the length of the stationary vertical hydraulic cylinder (4). As can be seen here, the movement of the piston (2) will pull the rod string (1) that has been attached to the pumping shaft, thus causing the extraction pump to move up and down.

Using the polished rod of the rod string (1) as a piston shaft (2) allows the height of the drive unit to be the same as that of the unit's maximum stroke length, unlike other currently available hydraulic drive units where the piston shaft is a separate element of the drive unit that pokes out of the top or bottom of the hydraulic cylinder (4) when the piston (2) is at its highest elevation.

FIG. 2 shows a preferred implementation of the drive unit, in which six tanks (5) filled with a compensation fluid, such as nitrogen, are distributed around the hydraulic cylinder (4), which helps the piston (1) movement control system. This enhances the stability of the hydraulic cylinder (4).

FIG. 3 shows a preferred way to attach the rod string's polished rod (1) to the piston (2) of the pump drive unit in this invention. The fitting includes two flanges, an upper flange (6) or hydraulic cylinder flange (4) which is supported on the seat (7 a) of a lower flange (7) or well-connection flange, fastened with bolls inserted into threaded holes (8).

In order to actuate the piston (2), fluid goes into the chamber (9), which will force the piston (2) to go up or down, depending on the pressure in the chamber (9).

FIG. 3 shows the seal assembly with its body (11), strung in the rod string's polished rod (1) and resting on the seat (21) of the lower flange (7), which includes: a guide ring (12) in contact with the piston (2) and a housing (13) under the guide ring with a first hydraulic seal, and next to it a guide bushing (14); under the guide bushing, there is a cavity (15) that makes up a second stage of the hydraulic seal. Under the second seal stage, in the body (11) of the seal assembly, there is a third hydraulic seal stage (16) that can separate hydraulic fluid from extraction fluid, in which there are also wipers (22), the cleaning elements of the rod string's polished rod (1), preventing any soil from getting to the remaining elements of the body (11) of the seal assembly. Schematically speaking, at the end of the rod string's polished rod (1) there is a part (17) that serves to stop the piston (2).

FIG. 4 shows the application where a spacer (18) is inserted in the rod string's polished rod (1); the spacer is located on top of the piston (2) and fastened with a threaded coupling (19) to the end of the rod siring's polished rod (1). Therefore, the desired spacing in the pumping unit is achieved by adding separators (18) between the piston (2) and the coupling (19) of the polished rod (1). The hydraulic seals shown in FIGS. 3 and 4 shall preferably be those known in the technical field as “polypack” seals.

With regard to the possible types of actuating fluids that can be used in this drive unit, they can be any of the fluids that are commonly used in the industry for moving pistons. 

Having described and specified the nature and scope of the invention and its implementation, exclusive rights and ownership are hereby claimed:
 1. Pump drive unit for water, oil or other fluid extraction able of providing a reciprocating motion (upward/downward) to a pumping unit through a pumping rod string (a); the drive unit includes a piston (2) that slides up and down inside a vertical hydraulic cylinder (4) as a result of the application of an actuating fluid, characterized in that the piston shaft (2) is the sucker rod string's polished rod (1).
 2. Pump drive unit for water, oil or other fluid extraction in accordance with claim 1, characterized in that the coupling of the piston (2) to the polished rod (1) of the pumping string (1) includes a lower well connection flange (7) with a seat (7 a) against which rests an upper flange (6) for the hydraulic cylinder (4), and in which said upper flange (7) has a tab (20) to support the hydraulic cylinder (4); located on the lower flange (7) and threaded into the polished rod (1) of the rod string there is a seal assembly.
 3. Pump drive unit for water, oil or other fluid extraction in accordance with claim 2, characterized in that the seal assembly includes a body (11) housing a guide ring on the top (12) in contact with the piston (2); underneath the guide ring there is a housing (13) with a first hydraulic seal, and next to it a guide bushing (14); under the guide bushing (14), there is a cavity (15) that makes up a second stage hydraulic seal; below this second hydraulic seal stage there is a third hydraulic seal stage (16) in the body (11) of the seal assembly that can separate the hydraulic fluid from the extraction fluid in which there are also wipers (22) for the rod string's polished rod (1).
 4. Pump drive unit for water, oil or other fluid extraction in accordance with claim 1, characterized in that at the end of the rod string's polished rod (1) and over the piston (2) there is at least one spacer (18) attached by a coupling (19) threaded to the end of the rod string's polished rod (1). 